Method for identifying kidney allograft recipients at risk for chronic injury

ABSTRACT

A method for identifying a renal allograft recipient at risk for chronic allograft damage or interstutial fibrosis and tubular atrophy (IF/TA) by comparing the transcription level of a preselected gene signature set with the transcription level of a comparison standard, and diagnosing the recipient as being at risk for chronic allograft damage if the transcription level of the preselected gene signature set is significantly higher than the transcription level of the comparison standard.

FIELD OF THE INVENTION

The present invention pertains to methods for identifying kidney allograft recipients at risk for chronic injury and a kit for use in the invention. The methods comprise analyzing transcriptome signatures obtained from early biopsies of stably functioning kidney allografts in order to identify and treat such patients.

BACKGROUND OF THE INVENTION

Kidney transplantation is the most common solid organ transplant performed in the US; more than 16,000 transplants were performed in 2010 (2011 SRTR data report). Despite a reduced incidence of acute rejection, improvements in long-term allograft survival have not been realized (1-2).

Chronic allograft damage (CAD), or interstitial fibrosis and tubular atrophy (IF/TA) of unknown cause is the major determinant of graft loss after the first year of transplantation (3). Clinical and histological events associated with IF/TA are poorly predictive of graft loss (4), making it difficult to identify allografts which may benefit from early interventions to prevent progression of fibrosis. Allograft biopsies in response to renal dysfunction remain the current diagnostic approach to chronic injury, by which stage irreversible fibrosis has developed. There is substantial evidence that pathological changes in the renal allograft predate functional changes (5). Protocol biopsies have suggested that upwards of fifty percent of grafts with stable renal function have evidence of IF/TA by 1 year (6). The development of a predictive assay to identify at risk grafts early after transplantation is essential to design targeted therapeutic interventions. The present inventors have learned that molecular changes obtained from protocol biopsies conducted early after transplantation predate the development of fibrosis. Pursuant to the present invention, a predictive gene set has been developed that identifies allografts at risk of progressive injury. This finding enables the identification of recipients at risk of graft loss at a time when therapeutic intervention may prevent IF/TA.

SUMMARY OF THE INVENTION

A 13 gene set has been identified that is independently predictive for the development of fibrosis at 1 year and early graft loss. The high predictive capacity of the gene set (AUC 0.947) was superior to clinical indicators (AUC 0.78). Routine histological parameters failed to identify histologically normal allografts in which fibrosis progressed, while the predictive gene set accurately discriminated and identified histologically normal allografts in which fibrosis ultimately progressed (AUC=0.987). The 13-genes also predicted early graft loss accurately (AUC-0.86 & 0.83 at 2- & 3-yrs respectively). The predictive value of this gene set was validated using an independent cohort and two independent, publicly available, expression datasets.

The gene set obtained at 3 months from stably functioning renal allografts correlated with the progression of established markers for chronic allograft damage at 12 months and proved superior to clinico-pathological variables currently used in clinical practice to identify renal transplant recipients at risk of allograft damage and loss.

In one aspect, the present invention provides a method for identifying a kidney allograft recipient at risk for chronic allograft damage comprising the steps of providing a biopsy specimen from a renal allograft obtained at 3 months post transplantation.

In a further aspect, the present invention provides primers for a selected 13 gene signature set comprising the genes KLHL13, KAAG1, MET, SPRY4, SERINC5, CHCHD10, FJX1, WNT9A, RNF149, ST5, TGIF1, RXRA and ASB15.

In a further aspect the invention provides a method of selecting a renal allograft recipient for treatment to reduce the risk of chronic allograft damage or IF/TA by comparing the transcription level of a preselected gene signature set obtained from the allograft with the transcription level of a comparison expression library, and selecting the patient for treatment for allograft rejection or damage if the transcription level of the preselected gene signature set is significantly higher than the transcription level of the comparison standard.

In another aspect the invention provides a gene signature set for identifying patients at risk for chronic renal damage or IF/TA comprising the genes KLHL13, KAAG1, MET, SPRY4, SERINC5, CHCHD10, FJX1, WNT9A, RNF149, ST5, TGIF1, RXRA and ASB15.

In a still further aspect, the present invention provides a kit for identifying renal allograft recipients at risk for chronic allograft damage comprising in separate containers comprising primers for a 13 member gene signature set, buffers, three housekeeping genes and negative controls and instructions for use

These and other aspects of the present invention will be apparent to those of ordinary skill in the art in light of the present specification, claims and drawings.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, the term “about” or “approximately” usually means within an acceptable error range for the type of value and method of measurement. For example, it can mean within 20%, more preferably within 10%, and most preferably still within 5% of a given value or range. Alternatively, especially in biological systems, the term “about” means within about a log (i.e., an order of magnitude) preferably within a factor of two of a given value.

Disclosed herein is a prospective study of serial protocol biopsies at predefined time points with unique and detailed clinical, histological, and molecular data sets. A gene set (the gene signature set, KLHL13, KAAG1, MET, SPRY4, SERINC5, CHCHD10, FJX1, WNT9A, RNF149, ST5, TGIF1, RXRA, ASB15) obtained at 3 months post transplantation from stably functioning renal allografts has been identified and validated. This gene set can be used to predict the progression of chronic allograft damage. This molecular risk gene signature has been found to be superior to clinico-pathological variables in identifying renal transplant recipients at risk for histological progression to graft injury in several patient cohorts and graft loss in a publically available cohort. The present invention provides a method for identifying renal allograft recipients at risk for chronic allograft injury which employs a a selected gene signature set as described herein. Allograft recipients having an increased expression of the 13 member signature set are at risk for chronic allograft injury. The present invention provides materials and methods to identify such patients as set forth herein.

The natural history of chronic allograft injury has revealed an early and rapid histological deterioration by 12-months post transplant (3). The presence of adverse histological changes (fibrosis and/or inflammation) at 12-months was then correlated with adverse long-term allograft outcomes in standard- and low-risk kidneys (14-16). Specifically, a Chronic Allograft Damage Index score at 12 months (CADI-12) of ≧2 has identified recipients at risk for graft loss at 3-years in the cohort descrbed herein, and from prior publications (5, 17). Owing to the more gradual histological deterioration observed in allografts after 12-months, interventions in immunotherapy once chronic allograft damage is established are less likely to alter outcomes (3).

While earlier time-point allograft histology has been correlated with the progression of Chronic Allograft Neuropathy (CAN) and allograft loss (18), clinico-pathologic variables that classify allografts into those at-risk for early histological deterioration and later graft loss, with even moderate sensitivity, have not been identified. For instance, while 60% of the cohort had low CADI scores (0-1) at 3 months, more than half of the patients with histological progression of allograft damage by 12-months belonged to this group, and were unidentifiable at 3-months by histology alone. Progression of Banff scores (6) within the first year without detectable changes in creatinine have also been noted (19). Conversely, histological changes observed at 3 months have been reported to reverse by 12-month assessments(20).

In the cohort disclosed herein, 40% of allografts with high CADI-3 had improved to CADI-12 of 0-1. Therefore, a significant clinical application of the 13-member gene signature set of the present invention is the ability to identify kidneys at risk for CAN development and progression, currently not identifiable by clinico-pathological parameters alone, at a stage when they are amenable to interventions. Furthermore, as opposed to a “one size fits all” immunosuppression strategy, the gene set herein has the potential to stratify low-risk allograft recipients who may then benefit from lowered immunosuppression.

As has been shown by many groups, the causes of chronic kidney allograft injury are diverse and cumulative (3, 15). This is reflected in the relatively large number of genes that were associated with adverse allograft outcomes in the 2 prior art validation cohorts. Einecke et al, identified a tissue gene signature (886 genes related to tissue injury, TGF-β effects) that was predictive of graft loss in for-cause allograft biopsies performed between 1-31 years post transplant8. A 601 probe-set signature from 6-month protocol biopsies in low-risk pediatric recipients, showed upregulation of immune response genes in patients who had histologic progression compared to those who did not (9). The 13-gene signature set of the present invention was validated with high predictive value in all of these cohorts with an ability to predict allograft outcomes despite differences in demographics, timing of biopsies post-transplant, presence of preexisting fibrosis and the respective endpoint studied (Table 9). Additionally, these two prior art studies used a limited gene set based on previous data or predicted pathological pathways. In contrast, an all-inclusive, non-hypothesis driven approach facilitated by sample size and based on the multifaceted nature of chronic injury was taken. Since CADI-12m is an ordinal variable, the initial gene list was derived based upon a signal of correlation, higher gene expression at 3-months and correlation with CADI-12, rather than a comparison between gene-expression in 2 well-defined clinical cohorts, as in previous studies. The method of the present invention increases the robustness of the identified relation and enhances the clinical application in undefined cohorts.

The addition of clinical predictors predictive of high CADI-12 (donor age, recipient gender, deceased donor organ, and acute rejection within 3 months of transplant) did not significantly enhance the performance of the gene set in predicting CAN. Subclinical rejection, predominantly borderline, was present in 20 of the 3 month biopsies. Additional analysis in which patients with acute cellular rejection (ACR) or i+t (the combined score for inflammation (i) and tubulitis (t))>2 were excluded clearly demonstrated that inflammation was not the predominant driver for the identified 13-gene signature set with the AUC remaining 1 (data not shown). The novel, non-biased approach used herein has thus identified a risk gene signature that differentiates allografts at risk for histological progression in the cohort. This invention bears wider applicability to identify at-risk kidneys as suggested by its validation in predicting allograft injury and failure in a variety of patient cohorts in whom biopsies taken at different time points post-transplant with and without pre-existing damage.

Protocol biopsies on stably functioning allografts provide a window into pathogenetic mechanisms that are initiated prior to the development of detectable allograft dysfunction. Ongoing subclinical rejections, polyomavirus BK infection, Calcineurin Inhibitor (CNI)-toxicity and antibody-mediated damage—processes that contribute to CAN which when detected can be intervened upon—may be identified (24-26). However, other studies have been unable to demonstrate significant differences in allograft outcomes with interventions performed on detected subclinical phenomena (27). This disparity may reflect the limitations of using histology alone while interpreting protocol biopsies, which may be influenced by inter-observer and sampling variability. On the other hand, 3- and 6-month protocol biopsy transcriptome changes that correlated with allograft histology at 12-months (11, 28), and a 12-month allograft gene signature that was correlated with allograft loss (15), have all been reported. As disclosed herein the genes whose expressions correlated with 3- or 12-month CADI were identified by Spearman correlations analysis and then were subjected to overall Gene Ontology enrichment. The Gene Ontology (GO)functions/pathways associated with CADI-correlated genes from correlation analysis were also validated with Gene Set Enrichment Analysis (GSEA) (9).

In one embodiment, the present invention is directed to primers for RT-PCR for the 13 member gene signature sequence. In another embodiment, the present invention is directed to a kit for identifying allograft recipients at risk for renal allograft injury comprising a container having therein primers for RT-PCR for a 13 member gene signature set and instructions for use. In a further embodiment the kit comprises a first container having therein primers for RT-PCR for a 13 member gene signature, a second container having therein primers for housekeeping genes, a third container having therein a buffer solution and instructions for use. Patients are stratified based on expression and those with high expression of the 13 gene signature set are diagnosed as being at risk for chronic allograft damage, and are thereafter treated to prevent such damage. Pursuant to the present invention, patients with high expression of the 13 genes can be identified using, for example, Real Time PCR, Nanostring or miSeq. In each case a standard is generated as the baseline for identifying patients at risk for chronic allograft damage or IF/TA.

Determination of Diagnostic Cut Off Using RT-PCR, Nanostring and miSeq

Using a training set of patients, mRNA from the biopsy sample will be analyzed for expression levels of the 13 gene signature set. Based on this expression data, a mathematical model will be developed to estimate the probability of patient developing fibrosis by one year. Patients will be stratified based on this score sensitivity/specificity, the positive predictive values (PPV) and negative predictive values (NPV) determined. Based on the PPV and the NPV an optimal cut off will be established which best categorizes the patients' risk for rejection. This may be a clear cut off into two groups in that if they are in the top group their expression levels are significantly higher and they have a high likelihood of developing fibrosis and the test is determined to be positive but if they are in the bottom they have a very low likelihood of developing fibrosis and the test is determined to be negative. In an alternative embodiment, the patients may be broken into tertiles based on their probability score determined as above. In this case if the patient is in (1) the top tertile, their expression levels are significantly higher and they have a high likelihood of developing fibrosis and the test is determined to be positive; (2) if they are in the second tertile or intermediate group their risk cannot be accurately determined; and (3) if they are in the bottom tertile they have a very low likelihood of developing fibrosis. and the test is determined to be negative.

The RT-PCR assay kit includes:

1) Primer container (16 tubes with one qPCR assay per tube for 16 genes including the 13-panel gene signature set of the present invention and housekeeping genes(ACTB and GAPDH) and the control probe 18s) . The assays were purchased from LifeTech. The primers are set forth below.

Primers for qPCR assay Assay ID (LifeTech ®) Availability Gene Symbol(s) Hs99999901_s1 — 18s rRNA Hs01060665_g1 INV* ACTB Hs02758991_g1 INV GAPDH Hs01067640_m1 INV RXRA Hs00243321_m1 INV WNT9A Hs00534909_s1 INV FJX1 Hs01006506_m1 INV KLHL13 Hs00698334_m1 INV SERINC5 Hs01935412_s1 INV SPRY4 Hs00704044_s1 INV KAAG1 Hs01565584_m1 INV MET Hs00395880_m1 INV ASB15 Hs00936461_m1 INV ST5 Hs01369775_g1 INV CHCHD10 Hs00411860_m1 INV RNF149 Hs00820148_g1 INV TGIF1 *INV = Inventory

2) TaqMan® Universal Master Mix II: reagents for qPCR reactions

3) TaqMan® ARRAY 96-WELL PLATE 6×16

4) Agilent AffinityScript QPCR cDNA Synthesis Kit: for the highest efficiency conversion of RNA to cDNA and fully optimized for real-time quantitative PCR (QPCR) applications

Experimental Procedure and Data Analysis:

Total RNA will be extracted from the allograft biopsy samples using Allprep kit (QIAGEN-ALLprep kit, Valencia, Calif. USA). cDNA will be synthesized using the AffinityScript RT kit with oligo dt primers (Agilent Inc. Santa Clara, Calif.). TaqMan qPCR assays for the 13 gene signature set, 2 house-keeping genes (ACTB, GAPDH) and 18s are purchased from ABI Life Technology (Grand Island, N.Y.). qPCR experiments will be performed on cDNA using TAQMAN universal mix and the PCR reactions will be monitored and acquired using an ABI7900HT system. Samples will be measured in triplicate. Cycle Times (CT) values for the 13 member signature gene set as well as the 2 housing genes will be generated. The ΔCT value of each gene will be computed by subtracting the average CT value for the house-keeping genes from the CT value of each gene and a penalized logistic regression fitting model using an logistf R package will be then applied on ΔCT values to derive the statistical model from which the probability score of high for each patient will be calculated.

${\log \frac{{p(x)}\;}{1 - {p(x)}}} = {{\beta_{0 +}^{*}\beta_{1}^{*}g_{1}} + {\beta_{i}^{*}g_{i}} + \ldots + {\beta_{13}^{*}g_{13}}}$

where (p(x) is the probability of high CADI, β*_(i) is penalized coefficiency and gi is the expression ΔCT of gene i)

Based on the probability score, prediction AUC, sensitivity/specificity, the positive (PPV) and negative predictive values (NPV) determined will determined. At a given specificity (90%), an optimal cut off will be established which best categorizes the patients risk for kidney fibrosis.

EXAMPLE A

An independent cohort of 45 cohort patients (18: CADI≧2, and 27: CADI<2) was used as the training set for qPCR assay. The RNA samples were extracted and subjected to qPCR experiments using this qPCR assay kit. After data acquisition and normalization, a penalized logistic model with following values (Table 1) was built and the prediction AUC on the training set was 0.866. The statistical model based on the training set will be used to predict the probability of kidney fibrosis for new samples and the probability score cutoff is 0.548 at 90% specificity.

TABLE 1 Parameters for penalized logistic regression model from qPCR training set β sd(β) lower95 upper95 Chisq (Intercept) −0.365 5.499985 11.1826 10.41205 0.005216 KLHL13 0.121359 0.121611 0.06046 0.514791 1.642695 MET −0.31735 0.247157 0.93868 0.066704 2.564086 KAAG1 0.279196 0.532691 0.75299 1.40152 0.266769 SERINC5 0.110388 0.492916 −0.785 1.022298 0.06097 CHCHD10 0.594793 0.513221 0.32058 1.637405 1.58411 SPRY4 −0.39334 0.721153 2.26251 0.839415 0.349045 FJX1 0.204501 0.33905 0.43074 0.932129 0.403804 RNF149 0.06954 0.457496 0.73284 0.898595 0.03126 ST5 0.740591 0.767047 0.48276 2.930863 1.272416 TGIF1 −0.40004 0.454692 1.32842 0.344652 1.089256 RXRA −0.28701 0.237485 0.76594 0.099958 2.098098 ASB15 −0.23106 0.173426 −0.6974 0.062775 2.251056

Nanostring Assay Kit:

Nanostring assay kit includes:

1) Custom CodeSet (barcoded probe sets for 13 gene panel including 3 house-keeping genes and negative controls provided by Nanostring) Pack

2) nCounter® Master Kit including nCounter Cartridge, nCounter Plate Pack and nCounter Prep Pack

3) QIAGEN RNeasy® Kit for extraction of high quality total RNA

Nanostring Experiments:

The total RNA will be extracted using QIAGEN RNeasy® Kit by following the manufacturer's protocol; Barcode probes will be annealed to the total RNA in solution at 65° C. with the master kit. The capture probe will capture the target to be immobilized for data. After hybridization, the sample will be transferred to the nCounter Pre Station and the probe/target will be immobilized on the nCouter Cartridge and the probes are then counted by the nCounter Digital Analyzer.

mRNA Transcriptomic Data Analysis

The raw count data from Nanostring analyzer will be processed in the following procedure the raw count data will be firstly normalized to the count of the house-keeping genes and the mRNAs with counts lower than the median plus 3 standard deviation of the counts of negative controls will be filtered out. Due to data variation arising from reagent lot, the count for each mRNA from different reagent lots will be calibrated by multiplying a factor of the ratio of the averaged counts of the samples on different reagent lots. The calibrated counts from different experimental batches will be further adjusted by ComBat package.

A penalized logistic regression fitting model using logistf R package will then be applied on normalized count values to derive the statistical model from which the probability score for each patient will be calculated.

The raw count data from the Nanostring analyzer will be processed in the following procedure: the raw count data will be first normalized to the count of the house-keeping genes and the mRNAs with counts lower than the median plus 3 standard deviation of the counts of negative controls will be filtered out. Due to data variation arising from reagent lot, the count for each mRNA from different reagent lots will be calibrated by multiplying a factor of the ratio of the averaged counts of the samples on different reagent lots. The calibrated counts from different experimental batches will be further adjusted by ComBat package.

A penalized logistic regression fitting model using logistf R package will be then applied on normalized count values to derive the statistical model from which the probability score of high likelihood for each patient will be calculated.

${\log \frac{{p(x)}\;}{1 - {p(x)}}} = {{\beta_{0 +}^{*}\beta_{1}^{*}g_{1}} + {\beta_{i}^{*}g_{i}} + \ldots + {\beta_{13}^{*}g_{13}}}$

where (p(x) is the probability of high CADI, β*_(i) is penalized coefficiency and gi is the count of gene i)

Based on the probability score, prediction AUC, sensitivity/specificity, the positive (PPV) and negative predictive values (NPV) will be determined. At a given specificity (90%), an optimal cut off will be established which best categorizes the patients risk for kidney fibrosis. This may be a clear cut off into two groups in that if they are in the top group they have a high likelihood of developing fibrosis and the test is determined to be positive but if they are in the bottom they have a very low likelihood of developing fibrosis and the test is determined to be negative. The alternative is that patients may be broken in to tertiles based on the above their probability score determined as above. In this case if the patient is in (1) the top tertile they have a high likelihood of developing fibrosis and the test is determined to be positive; (2) they are in the second tertile or intermediate group their risk cannot be accurately determined; and (3) they are in the bottom they have a very low likelihood of developing fibrosis and the test is determined to be negative.

MiSEQ Experiments:

MiSEQ assay kit will include:

1) Custom Assay (barcoded probe sets for 13 gene panel including 5 house-keeping gene panel)

2) Illumina® TruSeq® RNA Sample Preparation Kit v2

3) QIAGEN RNeasy® Kit for extraction of high quality total RNA

MiSEQ Experiments:

Total RNA will be extracted using QIAGEN RNeasy® Kit. The sequencing library will be generated using Illumina® TruSeq® RNA Sample Preparation Kit v2 by following manufacturer's protocol: briefly, polyA-containing mRNA will be first purified and fragmented from the total RNA. The first-strand cDNA synthesis will be performed using a random hexamer primer and reverse transcriptase followed by the second strand cDNA synthesis. After the end repair process, which converts the overhangs into blunt ends of cDNA, multiple indexing adapters will be added to the end of the double stranded cDNA. Next, PCR will be performed to enrich the targets using the primer pairs specific for the gene panel and house-keeping genes. Finally, the indexed libraries will be validated, normalized and pooled for sequencing on the MiSEQ sequencer.

mRNA Transcriptomic Data Analysis

The raw RNAseq data generated by MiSEQ sequencer will be processed using the following procedure: The reads with good quality will be firstly aligned to several human reference databases including hgl9 human genome, exon, splicing junction and contamination database including ribosome and mitochondria RNA sequences using the well-known BWA alignment algorithm. After filtering reads mapped to the contamination database, the reads that are uniquely aligned with a maximal 2 base mis-matches to the desired amplicon regions will be then counted as expression level for the corresponding gene and further subjected to quantile normalization across samples after log 2 transformation

A penalized logistic regression fitting model using logistfR package will be then applied on normalized count values to derive the statistical model from which the probability score of high likelihood for each patient will be calculated.

${\log \frac{{p(x)}\;}{1 - {p(x)}}} = {{\beta_{0 +}^{*}\beta_{1}^{*}g_{1}} + {\beta_{i}^{*}g_{i}} + \ldots + {\beta_{13}^{*}g_{13}}}$

(where (p(x) is the probability of high CADI, β*_(i) is penalized coefficiency and gi is the count of gene i). Based on the probability score, prediction AUC, sensitivity/specificity, the positive (PPV) and negative predictive values (NPV) will be determined. At a given specificity (90%), an optimal cut off will be established which best categorizes the patients risk for kidney fibrosis. This may be a clear cut off into two groups in that if they are in the top group they have a significantly higher transcription level of the 13 member gene signature set and have a high likelihood of developing fibrosis and the test is determined to be positive but if they are in the bottom they have a very low likelihood of developing fibrosis and the test is determined to be negative. The alternative is that patients may be broken in to tertiles based on the above their probability score determined as above. In this case if the patient is in (1) the top tertile they have a significantly higher transcription level of the 13 member gene signature set and a high likelihood of developing fibrosis and the test is determined to be positive; (2) they are in the second tertile or intermediate group their risk cannot be accurately determined; and (3) they are in the bottom they have a very low likelihood of developing fibrosis and the test is determined to be negative.

The development of a predictive gene set that identifies those patients early after transplantation who are at increased risk of progressive graft injury has several applications: individualizing therapy based on risk profile including targeting “at-risk” individuals for early individualizing therapy based on risk profile including targeting “at-risk” individuals for early intervention and minimizing therapy in those with good prognosis. In addition, it can be used for risk stratification in clinical trials allowing for novel therapeutic regimens to be tested in targeted populations.

In summary, a gene signature from protocol biopsies of stably functioning renal allografts at 3-months has been developed and validated. The gene signature identifies kidney allograft recipients at risk for histological deterioration and functional decline byl2-months. This gene signature was externally validated to predict allografts that sustained diverse adverse outcomes, representing kidneys at-risk in the intermediate and long term. The gene signature also has the potential to identify lower risk allograft recipients who may benefit from less intense

The present invention is directed to methods for identifying kidney allograft recipients who are at risk for developing chronic allograft injury, expressed as interstitial fibrosis and tubular atrophy (IF/TA). Patients can be monitored at 3, 6, 9, 12 months, and yearly thereafter. When patients are identified as being at risk for developing chronic allograft injury , the present invention includes methods for treating such patients. Treatment approaches would be as follows: in patients identified as high risk for chronic allograft fibrosis with low immunological risk as determined by parameters including absence of the acute rejection, subclinical rejection including boarderline sublinical rejaction on biopsy as defined by Banff Criteria (American Journal of Transplantation 2008; 8: 753-760), donor specific antibodies, and a low calculated Panel Reactive Antibodies (PRA—a measure of anti HLA antibodies), the methods include, without limitation, withdrawal of the calcineurin inhibitor (CNI), such as cyclosporine or tacrolimus, and substitution with a less fibrogenic immunosuppressive drug such as belatacept or sirolimus.; and, in those patients identified as high risk for chronic allograft fibrosis with subclinical rejection including boarderline sublinical rejaction on biopsy as defined by Banff Criteria (American Journal of Transplantation 2008; 8: 753-760), since subclinical rejection can contribute to the development of fibrosis, the methods include, without limitation, increase in immunosuppression such as an increase in the dose of calcineurin inhibitor (CNI), such as cyclosporine or tacrolimus or addition of another agent such as prednisone or mycophenolate mofetil.

In addition, patients that are identified as being at risk for developing chronic allograft injury can be treated with anti-fibrotic agents such as Pirfenidone, relaxin, Bone morphogenetic protein 7 (BMP-7), Hepatic growth factor (HGF) 6.

The present invention is described below using examples which are intended to further describe the invention without limiting the scope thereof

In the examples below, the following materials and methods were used.

Patient Population and Biopsy Specimens

Exclusion criteria for patients described herein included a positive T/B-CDC cross-match, desensitization for donor-specific antibodies, pediatric recipients and inability to give consent. Protocol renal allograft biopsies were obtained at 0, 3, 12, and 24 months post-transplant in 3 sites, and 0 and 24 months in 2 sites. Three-month protocol biopsies were performed on 244 patients, 204 of which had a corresponding 12-month biopsy. Microarray was performed on the first 159 3-month protocol biopsies hereinafter “m3_Bx”) and the remaining 45 were used for validation.

Data Collection

Donor and recipient data was collected at baseline. Donor information included donor age, race, gender, HLA, cause of death, status living versus deceased (SCD, ECD, or DCD). Recipient data included age, gender, race, cause of End Stage Renal Disease (ESRD) HLA, PRA, anti-HLA antibodies, Cold Ischemic Time (CIT) , Delayed Graft Function (DGF), induction and maintenance immunosuppression, cytomegalovirus (CMV) status, Hepititis C virus (HCV) and Hepititis B virus (HBV) status, duration 3, 6, 12 and 24 months, including physical exam, current infections, lab results (CBC, BUN, creatinine, metabolic panel and immunosuppression levels). In addition, clinical data were collected when a clinically indicated biopsy was performed.

HLA Antibody Screening

Serum was assayed for circulating anti-HLA antibodies at baseline using One Lambda Labscreen® beads (One Lambda Inc, Canoga Park, Calif.). A Mean Fluoroscence Intensity (MFI)>1000 was considered positive. The samples were analyzed on a Luminex LabScan 200™ using HLA Fusion software. Donor specific antibodies (DSA) were determined using the donor and recipient HLA typing. Patients with preformed DSA requiring desensitization protocols prior to or at the time of transplant were excluded from the study.

Histopathology and Diagnostic Classification

Two tissue cores were taken from each of the 3-month and 1 year protocol renal biopsies of the study cohort. One core was processed for histology and the other core was processed for mRNA. When only one core could be obtained priority was given to mRNA.

Renal biopsies were processed and read centrally. Formalin-fixed, paraffin-embedded sections were processed for histologic stains (hematoxylin and eosin, periodic acid Schiff, trichrome and Weigerts elastic stains). Immunohistochemistry for C4d was done on an automated stainer on paraffin sections stained with a rabbit polyclonal antibody (American Research Products, Inc.). All slides were scanned with a whole slide scanner (Aperio CS) and high-resolution digital images were archived in an image database.

Biopsies were evaluated and scored separately by 2 renal pathologists, without knowledge of the clinical data, using the well known Revised Banff 2007 Classification for Renal Allograft Pathology (6). Where diagnoses were discordant, a meeting was held with a third pathologist for a consensus diagnosis. Scoring was done on the whole slide images for all cases. Scores were entered into a custom Filemaker Pro database that calculated the Banff categories and Chronic Allograft Damage Index (CADI).

Microarray Experiments, Data Analysis and Cross-Validation

The details of micorarray experiments and data analysis are described below. Briefly, total RNA samples from biopsy samples were extracted and were subjected to microarray experiments using the Affymetrix human exon 1.0 ST array. The intensity data at gene level were extracted with RMA algorithm 7 and corrected for the experimental batch effect using the open source ComBat R package 8 after quality assessment. The genes whose expressions correlated with 3- or 12-month CADI were identified by Spearman correlations analysis and then were subjected to overall Gene Ontology enrichment. The GO functions/pathways associated with CADI-correlated genes from correlation analysis were also validated with Gene Set Enrichment Analysis (GSEA) (9).

To identify a minimal gene set to predict future kidney fibrosis, a focus gene set was employed. The gene set was specifically associated with 12 month CADI as determined by 100 time randomization analysis followed by correction for confounding clinical parameters (CIT, Deceased Donor, Donor Age, Anti HLA antibodies, Acute rejection). An optimal gene set with the best prediction AUC score was identified after 5000 iterations of a fitting penalized logistic regression model on the focus geneset. The gene set was cross-validated using a 3-fold cross-validation method with 100-iterations on our data. The gene set was further validated by quantitative Polymerase Chain Reaction (qPCR) on an independent patient cohort, and also by analysis on three independent publicly available datasets from different array platforms (11-13). Microarray expression files are posted on the Gene Expression Omnibus website (GSE).

Statistical Analysis of Clinical Data

Descriptive statistics (means and standard deviations) were used to summarize the baseline characteristics of donors and recipients, and were compared between study groups (high CADI-12 vs low CADI-12, progressors vs non-progressors) using the chi-square test and Fisher's exact test. Univariate comparisons of continuous variables were done using an unpaired T-test (Mann-Whitney test for corresponding non-parametric analysis). Kaplan-Meier curves were plotted for the duration of the study, with graft loss (not censored for death) as outcome. Survival curves of different groups were compared using the Log-rank test and Gehan-Breslow-Wilcoxon tests. P<0.05 was considered significant (GraphPad Prism version 5.03, Graphpad inc, La Jolla, Calif.). To determine the predictive factors for having a high CADI (score≧2) at twelve months post-transplant, multiple logistic regression using backwards predictor selection was performed. The predictors assessed were: donor age, donor race, donor gender, donor status, acute rejection before 3 months, recipient race, recipient gender, expanded criteria donor, induction and maintenance immunosuppressive therapy and the presence of anti HLA antibodies. Cold ischemia time and delayed graft function were considered in a subgroup analysis that included deceased donors only. Logistic models using the same predictors were built to assess predictive factors of progression by month 12 in the full transplant population and the deceased donor only population. All analyses were completed using SAS version 9.2 (SAS, Cary, N.C.).

Supplementary Methods

Clinical Data Collection

Donor and recipient data were collected at baseline. Donor information included age, race, gender, HLA genotype, cause of death, and allograft status (i.e. SCD, ECD, or DCD). Recipient data included age, gender, race, cause of ESRD, HLA genotype, PRA, presence and type of anti-HLA antibodies, cross match status, cold ischemia time (CIT), delayed graft function (DGF), immunosuppression regimen, CMV status, HCV and HBV status, dialysis vintage, dialysis modality, transfusion history, pregnancy history, and previous transplants.

Histopathology:

Two tissue cores were taken from each of the 3-month and 1 year protocol renal biopsies of the Genomics of Chronic Allograft Rejection (GoCAR) cohort. One core was processed for histology and the other core was processed for mRNA. When only one core could be obtained priority was given to mRNA at 3-months and to histology at 12-months. Renal biopsies were processed and read centrally. Formalin-fixed, paraffin-embedded sections were processed for histologic stains (hematoxylin and eosin, periodic acid Schiff, trichrome and Weigerts elastic stains). Immunohistochemistry for C4d was done on an automated stainer on paraffin sections stained with a rabbit polyclonal antibody (American Research Products, Inc.). All slides were scanned with a whole slide scanner (Aperio CS) and high-resolution digital images and archived in an image database.

Biopsies were evaluated and scored separately by 2 renal pathologists, without knowledge of the clinical data, using the Revised Banff 2007 Classification for Renal Allograft Pathology 1 (SIS reference). Where diagnoses were discordant, a meeting was held with a third pathologist for a consensus diagnosis. Scoring was done on the whole slide images for all cases. Scores were entered into a custom Filemaker Pro database that calculated the Banff categories and Chronic Allograft Damage Index (CADI). The CADI-score is a composite score that includes six histologic components—vascular intimal sclerosis (cv), tubular atrophy (ct), interstitial fibrosis (ci), interstitial inflammation (i), mesangial matrix increase (mm) and glomerusclerosis (g). Each component is scored between 0 & 3, giving a maximum possible score of 18. CADI-scores in protocol biospies has been validated to directly correlate with outcomes by several authors2-3.

Microarray Experiments

Total RNA was extracted from percutaneous allograft biopsy samples obtained at 3 month after transplantation using All prep kit (QIAGEN-ALLprep kit, Valencia, Calif. USA) and was stabilized with RNA-later(Qiagen, Inc). RNA quality was assessed using Bioanalyzer 2100 (Agilent Technologies). Samples with an RNA Integrity Number greater than eight were used in subsequent microarray experiments. Affymetrix mouse exon 1.0 ST arrays were used following standard protocol provided by the manufacturer (Affymetrix Inc.). In brief, ENCORE amplification and labeling kit (NuGen, San Carlos, Calif.) was applied to the first batch of samples starting with approximately 100 ng of total RNA to generate biotin-labeled RNA fragments for hybridization to the chip. For samples with a low RNA concentration, the Nugen Ovation PICO amplification kit (NuGen, San Carlos, Calif.) was applied. The chips were scanned using GeneChip Scanner 7G (Affymetrix Inc.).

Microarray Data Processing

The intensity data of microrray experiments at the gene level were extracted and summarized with the RMA algorithm4. Data quality was assessed using the Affymetrix Expression Console (Affymetrix Inc). The Affymetrix control probesets and probesets with low intensity across all samples were excluded from downstream analysis. Batch effects were adjusted using the ComBat R package5.

Bioinformatic Analyses

The workflow of bioinformatic analysis was performed with statistical R packages. The goal of analyses was to derive a relatively robust set of genes (˜10-20) that predicts the development of chronic allograft nephropathy.

Identification of the Allograft Transcriptional Signature:

Spearman correlation analyses were performed on the 3-month allograft gene expression data for 3-month allograft CADI score (CADI-3) as well as 12-month CADI score (CADI-12). The correlation coefficient and the p-value for the relationship between the level of expression and CADI score were calculated for each gene. The slope of gene expression against the CADI score was also computed using a linear regression model. Genes with a p value of <0.05 were selected. Two lists of genes with p<0.05 were generated corresponding to either the 3 month or 12 month CADI scores Annotated functional and molecular mechanisms of these two lists of genes were determined by Gene Ontology (GO) enrichment analysis based on Fisher-exact test. Alternatively, the gene expression dataset was analyzed to determine biological functions that are enriched in biopsies with higher CADI scores. To accomplish this, we applied Gene Set Enrichment Analysis (GSEA) (6-7) to the entire microarray dataset and determined gene functions that are enriched in samples with a high CADI score (CADI≧2) versus those with a low CADI score (CADI<2). Top GO terms associated with both the high and low CADI groups were determined, and compared to the results of GO enrichment analysis derived from the analyses of correlation between gene expression level and CADI score described above.

Prediction Analysis:

To derive a more significant and focused gene set from the large list of genes that have statistically significant association with CADI scores, the gene list was filtered by applying various statistical prediction models. First, the whole cohort of patients was randomly assigned to 2 groups in a 1:1 ratio. Spearman correlation analysis was applied to determine the genes with expressions levels that correlated with the severity of CADI score at 3 and 12 months. The 1:1 randomization was repeated 100 times and correlation analysis of gene expression with CADI score at 3 and 12 month was performed for each of the 100 iterations. Genes that occurred more than twice in the 100 iterations of randomization with a correlation at a P<0.05 with CADI in both groups were considered as a focused gene set from which a minimal prediction set was identified for predicting kidney fibrosis. Genes that were exclusive to the CADI-12 focus gene set (i.e. genes not shared with the CADI-3 focus gene set) were derived and further filtered by correction for clinical confounders (donor age, living vs deceased donor, donor gender and race, CIT min, induction therapy, anti HLA class I, and II antibodies) using multiple linear regression analysis, as well as exclusion of genes with a low median log 2 intensity of less than 5.

Finally, iterative logistic model fitting (5000 iterations) was performed in order to identify an optimal and minimal gene set for prediction of future kidney fibrosis. Initially, 20 genes were randomly selected from the filtered CADI-m12 focus gene set. The expression data of the 20-gene group was fitted into the penalized logistic regression model for prediction of high (CADI≧2) and low (CADI<2) CADI. The genes with significant association with high/low CADI (p<0.05) were identified from the regression model for each of the 20-gene group. The steps above were repeated 5000 times. Statistically significant genes (P<0.05) were identified from each iterative operation. The occurrence of significant genes from the 5000 iterations was calculated. Finally, the top 40 genes ranked by the number of occurrences were applied back to the penalized logistic regression model for high vs. low CADI prediction. Statistically significant genes (P<0.05) using this model were considered the final optimal gene set. The AUC score and sensitivity and specificity were calculated from logistic regression model using the final optimal gene set. The receiver operating characteristic curves of the final optimal gene set was compared to randomly selected gene sets of equal size for predicting high vs. low CADI to demonstrate that the final optimal geneset gave the best prediction. In addition, 10000 randomly selected gene sets were selected and AUCs of these gene sets were calculated and compared to the AUC of the final optimal gene set.

The final optimal gene set was cross-validated using a 3-fold cross-validation method. Briefly, the patients were randomly divided into 3 groups of equal size and equal number of high and low CADI patients and the data for any two groups were used as the training set with the third as the prediction set. The penalized logistic regression model that was built on the training set was applied on the prediction set to predict the outcome and the true and false positive rates. Prediction accuracy was calculated from the prediction data set and then averaged from three possible permutations. The steps were repeated over 100 times. The overall true or false positive rates and prediction accuracy were computed. The distribution of AUCs on the testing set based on the model derived using the training set for 100 iterations was plotted. To further assess the confidence of prediction, the group labels were randomly assigned to the patients and AUC were calculated on the group-label permuted data. The steps above were repeated 10000 times and the proportion of AUCs from 10000 iterations were higher than original AUC were calculated.

Prediction of high/low CADI at a different CADI-12 thresholds (high CADI-12≧3 or high CADI-12≧4) was also performed to assess the robustness of 13 geneset prediction. To investigate whether prediction by the gene set is superior to prediction by clinical variables, the multivariate logistic regression was performed for prediction of high/low CADI-12 by including the following demographic/clinical variables: CADI-3, Donor_Age, Deceased_donor, ECD_kidney, DGF, Gender,Race, CIT_min, Induction_Therapy, Anti_HLA_Ab_Class_I, Anti_HLA_Ab Class_II, Tacrolimus and CYA. After step-wise selection, the variables that remained significant were used in final model. The AUC for the ROC curve of the final model was then calculated and compared to CADI-12 prediction with the geneset. Lastly to check if the inflammation was the driver of 13 gene set, the prediction accuracy of acute rejection was evaluated at 12 month in 101 patients and high/low CADI-12 for the patients without acute rejection.

To test if the gene set could predict early graft loss post-transplant for the original 155 patients after exclusion of the 4 patients who died with a functioning graft, a logistic regression prediction model was firstly applied with the gene set among only those patients who either had graft loss within 3yr or had been followed-up for at least three years without graft loss and calculated the AUC. Secondly, survival analysis on all 155 patients was performed to examine if the gene set is associated with graft loss: Principle Components Analysis (PCA) on expression data for the 13 genes was initially performed and the top 10 principle components (PC) were applied to Cox proportional hazard model of time to graft loss. The principle components (PC) that were significantly associated with graft loss were selected (p<0.05) and the linear combination of eigenvalues of significant components multiplied by the coefficiencies of corresponding PCs from Cox model was used as the gene set risk score (GR-score). The demographic and clinical variables, including CADI-3, delayed graft function, acute rejection at 3month or prior, antibodies to HLA1 or HLA2, donor race, donor age, recipient race, recipient age, donor status (living/deceased), and induction therapy, alone or in conjunction with the gene set risk scores were fitted in Cox proportional hazard model of time to graft loss to investigator if any of the demographic or clinical variables are associated with graft loss. The patients were then stratified into two populations based on gene set risk score (GR-score) for Kaplan-meier survival analysis. Finally the time-dependent ROC for graft loss prediction within 2 or 3 yrs post-transplant was plotted and the AUCs calculated.

Validation of Gene Set:

The final optimal gene set was also validated on two independent public datasets. Both public datasets were on the Affymetrix GeneChip platform HU430plus2 (GSE213748, GSE259029). The raw data of these public datasets were processed in Affymetrix Expression Console similar to what is described above for the claimed data set. The expression data for each of the genes in the final optimal gene set was extracted. Predictions of clinical data (graft loss post biopsy at any time for GSE21374, and progressor/non-progressor based on CADI score for GSE25902) was performed using the penalized logistic regression model. AUC scores for each of these 2 data sets were calculated from the ROC curves for prediction specificity over sensitivity. Time to graft loss analysis on data set 1 was also performed (GSE21374) using the same approach as that for GOCAR dataset.

The optimal gene set was also applied to predict the progressors and non-progressors using the same approach described above. Patients who had CADI-3≦3 and demonstrated a ΔCADI≧2 by 12 month were considered as progressors, and those who had ΔCADI≦1 were considered non-progressors. Similar assessments were done for those with CADI score at 24 months and also for the patients with CADI-3≦2.

qPCR Example

Total RNA was extracted from allograft biopsy samples of 45 independent cohort patients (18: CADI≧2, and 27:CADI<2) using Allprep kit (QIAGEN-ALLprep kit, Valencia, Calif. USA). cDNA was synthesized using AffinityScript RT kit with oligo dt primers (Agilent Inc. Santa Clara, Calif.). TaqMan qPCR assays for the 13 geneset, 3 house-keeping genes (ACTB, GAPDH and RPLP0) and 18s were purchased from ABI Life Technology (Grand Island, N.Y.) . qPCR experiments were performed on cDNA using TAQMAN universal mix and PCR reaction was monitored and acquired using an ABI7900HT system. Samples were measured in triplicates. CT values for the prediction geneset as well as the 3 housing genes were generated. The ΔCT value of each gene was calculated by subtracting the average CT value for the house-keeping genes from the CT value of each gene and penalized logistic regression fitting model was then applied on ΔCT values for prediction of the high and low CADI in 45 patients and AUC score was then calculated as described above.

EXAMPLE 1 Patient Population and Graft Outcome.

588 patients were enrolled in the cohort; 204 patients were included in the current study based on inclusion criteria. When quantified using CADI scores, 60% of 12-month biopsies had a CADI of 0-1, 23% of 2-4, and 17% more than 4. As expected, CADI-12 negatively correlated with 12-month eGFR (r=0.35; p=0.0004), and CADI-12≧2 correlated with 3-year graft survival (log rank p=0.007); High CADI-12 was defined as ≧2 based on association with graft survival 5 10. Table 1 summarizes patient demographics based on CADI. In multivariate regression clinical factors significantly associated with high CADI-12 were donor age, recipient).

Microarray was performed on 159 m3_Bx, 101 of which had a corresponding 12-month protocol biopsy. Reasons for lack of 12-month biopsy included graft loss (n=8), death (n=1), lost-to-follow up (n=9), contraindication/inability to obtain biopsy (n=40). There was no difference in clinical variables between 159 microarray patients and the 101 with one-year biopsies (Table 1). 86 patients had a second m3 biopsy core available for pathology, 55% had CADI 0-1, 33% 2-3, and 12% CADI>3. Subclinical acute rejection was diagnosed in 20/86 (23.5%) m3_Bx [13-borderline, 3-IA, 1-IB, 3-IIA], while 52% were reported as normal.

EXAMPLE 2 Intragraft Molecular Phenotype is Time Dependent.

Gene expression profiles from m3_Bx were analyzed by correlation analysis and Gene Set Enrichment Analysis (GSEA) to understand molecular mechanisms of IF/TA (n=159). 1,316 genes were identified that significantly correlated with CADI-3 (806 positively and 510 negatively) and 1,056 genes with CADI-12 (852 positively and 204 negatively) at a cutoff unadjusted p<0.05,. Only 176 genes (13.2%) correlated with both CADI-3 and CADI-12. Gene Ontology enrichment indicated that the transcripts specifically associated with CADI-3 alone were related to alloimmunity, including T-cell activation; while genes involved in programmed cell death/apoptosis and cell adhesion were associated with CADI-12 alone . Biological functions were further confirmed by GSEA method in which gene expression data in GO category were compared between patients with high (≧2) and low (<2) CADI at 3- or 12-months.

EXAMPLE 3 3-Month Transcriptome Identifies Kidneys at Risk for Chronic Allograft Damage

The transcriptome obtained from m3_Bx was analyzed to identify a minimal gene set predictive of CADI-12 (Supplementary methods). Initially a 169 gene set that correlated specifically with CADI-12 but not CADI-3 was identified. These 169 genes were reduced to a set of 85 genes after excluding genes with a low intensity and adjustment for clinical parameters (Table 4). Iterative applications of penalized logistic regression fittings on expression data for these 85 genes identified an optimal 13 gene set that differentiated high CADI-12 from low CADI-12 with an area under the curve (AUC) of 1 (Table 2). This was higher than AUC's for randomly selected 13 gene sets from the initial 85 genes (mean AUC 0.87±0.025). The gene set was subjected to a 3-fold cross-validation method with random assignment to training and test sets (100 times). The average sensitivity, specificity and prediction accuracy for the test sets were 95% 82%, 86%, respectively. The average AUC for the 100 test sets [0.947 (95% CI: 0.942-0.952)] was higher than any AUC that was obtained from the prediction on randomly assigned high and low CADI patient groups with 10000 iterations. The AUCs obtained for CADI-12 at different cutoffs including CADI-12≧3 or ≧4 were 0.986 & 0.963 respectively, confirming the robustness of the gene set of the present invention. Prediction by the gene set was superior to clinico-pathologic variables (AUC=0.783), and combining clinical parameters predictive of high CADI-12 did not enhance the performance of the gene set. Importantly the gene set also accurately predicted fibrosis based on Banff score (Ci+Ct) (AUC=0.092). Subclinical rejection was present in twenty m3_Bx and, was associated with a high CADI-12 (p=0.0003) and BANFF score (Ci+Ct) (p=0.002). Excluding m3_Bx with rejection or i+t>2, did not alter the prediction of high CADI-12 by the gene set disclosed herein (AUC=1), while the 13 genes poorly predicted ACR (AUC=0.743). This taken in conjunction with the ability to predict Ci+Ct demonstrate that inflammation was not the predominant driver for its derivation. Lastly, when validated by qPCR on an independent GoCAR cohort with similar demographics as the training set (Table S4), the gene set accurately differentiated high vs. low CADI-12 (AUC=0.866).

EXAMPLE 4 Transcriptome Predicts Progression of Chronic Allograft Damage

Next, the gene set was applied to categorize m3_Bx with minimal or no fibrosis into those that would or would not develop progressive fibrosis. From the original 101 patients, those allografts with a CADI-3≦3 (n=68) were identified and two groups were characterized based on change in CADI from 3 to 12 months: (1) progressors (n=1) with ΔCADI≧2; and (2) non-progressors (n=51) with ΔCADI≦1 (Table 1). Table 5 compares 3- and 12-month biopsy pathology scores in progressors vs. non-progressors. Progressors had a higher CADI at 3 months predominantly driven by the ci score; however CADI-3 alone could not be used to differentiate progressor from non-progressor. Clinical parameters were also poor predictors of progression (AUC=0.642). The disclosed gene set accurately identified CADI-progressors from non-progressors (ΔCADI≧2) at both 12-months (AUC 0.984) and 24-month (AUC 0.859). Furthermore it predicted CADI-progression by 12- and 24-months equally well when pristine allografts with CADI-3<2 were analyzed (AUC=1 and 0.84, respectively). These findings are of clinical importance since progressors had poorer graft survival than non-progressors at 36-months follow-up (Gehan-Breslow-Wilcoxon p=0.01; Log-rank p=0.06;)

EXAMPLE 5 Transcriptome Signature Predicts Early Allograft Loss

Cox-models were next generated with the gene set of the present invention and clinical variables to predict death-censored graft loss on the disclosed cohort (graft loss n=11). Three principle components (P4, P6 and P7) of expression data of 13-genes were significantly associated graft loss in the Cox proportional hazard model (p<0.05)(Table S5) and used to derive the “gene set risk score” (GR-score) (Graft loss HR 2.719, 95% CI 1.60-4.63). Patients were stratified into two groups of equal size based on this GR-score and higher scores were significantly associated with graft loss (Log-rank p<0.002). Using the GR-score, AUC's for time-dependent graft loss within 2- & 3-yrs post-transplant were 0.863 and 0.849, respectively. Among clinical variables, only delayed graft function was significantly associated with graft loss (Table 6). However combination of gene set with delayed graft function did not improve prediction.

EXAMPLE 6 Validation of the Predictive Gene Set

To confirm the utility of the 13 gene set in diverse settings, two independent, publically available data sets were analyzed using the endpoints of graft loss and CADI as indicators of chronic allograft injury (Table 9). The gene set accurately predicted the relative endpoint for each of the data sets, outperforming the AUC reported by the original studies. Survival analysis for data set-1 using the gene set of the present invention showed significant differences between stratified high- and low-risk groups for graft loss (p=2.1e-9); AUC's for graft loss within 1- and 2-yrs after biopsy were 0.865 and 0.807, respectively. These data demonstrate that this 13 gene set can be applied across populations for the prediction of diverse yet clinically important outcomes including allograft survival.

EXAMPLE 7 13 Gene Signature Set Pursuant to Present Invention

KLHL13, KAAG1, MET, SPRY4, SERINC5, CHCHD10, FJX1, WNT9A, RNF149, ST5, TGIF1, RXRA, ASB15. The art recognized names of these genes is shown in Table 2.

TABLE 1 Demographic and clinical characteristics (High- and Low-CADI-12; CADI-Progressors and non-Progressors) 101 patients 51 Non- 159 patients in with High CADI Low CADI 17 Progressors Progressors microarray CADI-12 n = 40 n = 61 ΔCADI ≧2 ΔCADI <2 Mean ± SD Mean ± SD P- Mean ± SD Mean ± SD P- Mean ± SD Mean ± SD P- Characteristics (%) (%) value^(#) (%) (%) value^(#) (%) (%) value^(#) Recipient age 48.84 ± 13.27 46.90 ± 12.38 0.24 48.17 ± 13.32 47.36 ± 13.00 0.96 48.98 ± 14.34 46.83 ± 12.79 0.56 Recipient gender - 47 (29.35) 26 (25.70) 0.57 16 (40.00) 10 (16.67) 0.03 9 (52.94) 10 (19.61) 0.01 Female Recipient race 0.33 0.99 0.28 White 92 (57.86) 66 (65.35) 23 (57.5) 43 (70.50) 8 (47.05) 39 (76.47) African-American 37 (23.27) 15 (14.85) 6 (15.0) 9 (14.76) 4 (23.52) 5 (9.80) Hispanic 14 (8.82) 7 (6.93) 4 (10) 3 (4.91) 2 (11.76) 2 (3.92) Other/Unreported 16 (10.12) 13 (12.87) 7 (17.5) 6 (9.83) 3 (17.65) 5 (9.80) Recipient ESRD 0.52 0.63 0.90 diagnosis Diabetic 57 (35.85) 33 (32.67) 12 (30.0) 21 (34.42) 4 (23.52) 17 (33.33) nephropathy Hypertension 24 (15.09) 17 (16.83) 7 (17.5) 10 (16.39) 4 (23.52) 8 (15.69) Glomerulonephritis 28 (17.61) 22 (21.78) 7 (17.5) 15 (24.59) 3 (17.65) 10 (19.61) Polycystic Kidney 14 (8.82) 13 (12.87) 5 (12.5) 8 (13.11) 3 (17.65) 7 (13.72) Other 36 (22.64) 16 (15.84) 9 (22.5) 7 (13.11) 3 (17.65) 9 (17.64) Prior renal 4 (2.51) 2 (1.98) 1.00 2 (5) 0 (0) 0.15 1 (5.88) 1 (1.9) 0.45 transplant, n (%) Donor age 41.13 ± 16.80 40.73 ± 16.80 0.87 47.08 ± 17.91 36.57 ± 14.75 0.008 43.94 ± 17.80 37.47 ± 17.01 0.18 Donor gender - 77 (48.13) 46 (45.54) 0.70 17 (42.50) 29 (48.33) 0.69 5 (29.41) 24 (47.05) 0.17 Female Donor race 0.64 1.00 0.99 Caucasian 121 (75.6) 80 (79.21) 31 (77.5) 49 (80.32) 13 (76.47) 42 (82.35) African-American 17 (10.63) 8 (7.92) 4 (10.0) 4 (6.55) 2 (11.76) 3 (5.88) Hispanic 12 (7.54) 5 (4.95) 1 (2.5) 4 (6.55) 1 (5.88) 3 (5.38) Other/Unreported 9 (5.66) 8 (7.92) 4 (10.0) 7 (11.47) 1 (5.88) 3 (5.88) Doner status- 94/65 58/43 0.79 25/15 33/28 0.42 10/7 28/23 1.00 Deceased/Living 3-month Serum 1.39 ± 6.43 1.32 ± 0.38 0.26 1.321 ± 2947  1.325 ± 0.4326 0.96 1.36 ± 0.30 1.32 ± 0.30 0.66 Creatinine 3-month CADI- 1.63 ± 1.76 1.66 ± 1.79 2.57 ± 2.08 1.06 ± 1.28 <0.001 1.53 ± 1.18 0.86 ± 0.98 0.03 Mean ± SD - Median (IQR) 1 (3-0) 1 (3-0) 2 (3-1) 1 (2-0) 1.5 (3-0.25) 1 (1.5-0) Cold Ischemia time 14.64 ± 6.78  13.81 ± 6.74  0.46 15.63 ± 7.63 12.39 ± 5.11 0.05 16.32 ± 10.65 12.78 ± 5.147 0.17 (hrs)* h/o Delayed graft 21 (13.21) 9 (8.91) 0.32 7 (28.0) 2 (6.06) 0.009 4 (23.52) 4 (7.84) 0.17 function^(#) Anti-HLA 35 (23.17) 25 (26.59) 0.53 11 (28.20) 14 (25.45) 0.63 3 (33.33) 8 (13.68) 1.00 antibodies** DSA positive 11 (7.28) 7 (7.44) 3 (7.69) 4 (7.27) 3 (16.66) 4 (7.84) Class-I 8 (5.29) 6 (6.38) 3 (7.69) 3 (5.45) 3 (16.66) 2 (3.92) Class-II 6 (3.97) 2 (2.12) 0 (0.0) 2 (3.64) 0 (0.0) 3 (5.88) Non-DSA positive 25 (16.55) 20 (21.27) 8 (20.51) 12 (21.81) 0 (0.0) 6 (11.76) Class-I 25 (16.55) 20 (21.27) 8 (20.51) 12 (21.81) 0 (0.0) 6 (11.76) Class-II 13 (8.61) 7 (7.44) 3 (7.69) 4 (7.27) 0 (0.0) 4 (7.84) Induction therapy* 0.67 0.47 0.24 Thymoglobulin 49 (30.81) 26 (25.74) 12 (30.0) 14 (22.95) 5 (29.41) 9 (17.65) Anti-CD25 therapy 32 (32.70) 38 (37.63) 17 (42.5) 21 (34.42) 9 (52.94) 19 (37.25) Campath 9 (5.66) 8 (7.92) 2 (5.0) 6 (9.83) 1 (5.88) 6 (11.76) None 49 (30.81) 29 (28.71) 9 (22.3) 20 (32.78) 2 (16.67) 17 (33.33) 12-mocth 0.72 0.84 0.75 Maintenance immunosuppression MMF, CNI, steroids 139 (87.42) 90 (89.11) 37 (92.5) 53 (86.89) 16 (94.12) 44 (84.61) MMF, CNI 12 (7.35) 8 (7.92) 2 (5.0) 6 (9.84) 1 (5.88) 7 (13.46) Others 8 (5.03) 3 (2.97) 1 (2.5) 2 (3.27) 0 (0.0) 1 (1.92) 1-year acute 22 (13.84) 22 (21.78) NA 18 (45.00) 4 (6.36) <0.01 7 (41.18) 5 (9.80) <0.01 rejection Legend: CADI—chronic allograft damage index at 12-months; MFI—mean fluorescence intensity; MMF—mycophenolate mofetit; CNI—calcineurin inhibitors; DSA—donor-specific antibody; *Deceased donors only; **94/101 patients had HLA antibodies measured. ^(#)P value determined by Mann-Whitney test (non-parametric comparisons) or unpaired T-test.

TABLE 2 Multivariate analysis - Clinical covariates predictive of CADI-score at 12-months ≧2 Odds Ratio Estimates 95% Wald Point Confidence P- Effect Estimate Limits value^(#) Donor Age 1.062 1.025 1.100 0.0007 Donor status (DD *vs LD**) 4.292 1.311 14.054 0.0161 ACR (before 3-mths) (Yes vs No) 3.014 1.023 8.876 0.0453 Recipient race 1.709 0.591 4.947 0.3227 (non-caucasian vs Caucasian) Recipient_Gender 6.653 1.900 23.294 0.0030 (Female vs Male) Induction Therapy*** Lymphocyte depleting 1.445 0.408 5.111 0.8515 Lymphocyte non-depleting 2.550 0.660 9.855 0.1915 antiHLA antibodies (No vs Yes) 0.358 0.092 1.399 0.1397 ^(#)P-value - Wald Chi-square, * DD—Deceased donor, **LD—Living donor ***Induction therapy category compares Lymphocyte depleting and Lymphocyte non-depleting induction to No induction therapy

TABLE 3 13 Gene Prediction Set mRNA CADI ProbeID Symbol Gene Description Cytoband Accession Corr Pvalue 3326826 FJX1 four jointed box 1 (Drosophila) 11p13 NM_014344 0.384142 7.31E−05 4019160 KLHL13 kelch-like 13 (Drosophila) Xq23-q24 NM_001168302 0.380008 8.87E−05 3954887 CHCHD10 coiled-coil-helix-coiled-coil-helix domain containing 10 22q11.23 NM_213720 0.338868 0.000528 2864449 SERINC5 serine incorporator 5 5q14.1 NM_01174072 0.330535 0.000736 3020343 MET met proto-oncogene (nepatocyte growth factor receptor) 7q31 NM_001127500 0.325015 0.000912 2567583 RNF149 ring finger protein 149 2q11.2 NM_173647 0.304022 0.001996 2879105 SPRY4 sprouty homolog 4 (Drosophila) 5q31.3 NM_030964 0.303968 0.002 2898441 KAAG1 kidney associated antigen 1 6p22.1 NM_181337 0.264688 0.007476 3776504 TGIF1 TGFB-induced factor homeobox 1 18p11.3 NM_170695 0.248915 0.012071 2459352 WNT9A wingless-type MMTV integration site family, 1q42 NM_003395 0.237215 0.016917 member 9A 3361971 ST5 suppression of tumorigenicity 5 11p15 NM_005418 0.231432 0.019879 3021696 ASB15 aniyria repeat and SOCS box-containing 15 7q31.31 NM_080928 −0.2548 0.010128 3193339 RXRA retinoid X receptor, alpha 9q34.3 NM_002957 −0.30533 0.001904

TABLE 4 The 85 focus geneset ProbeID Gene Symbo Gene Description Cytoband mRNA Acc CADI Corr Pvalue Slope 2761842 PROM1 prominin 1 4p15.32 NM_00114 0.358 0.000 0.138 3040518 MACC1 metastasis associated in colon cancer 1 7p21.1 NM_18276 0.407 0.000 0.109 2583465 ITGB6 integrin, beta 6 2q24.2 NM_00088 0.340 0.000 0.102 2974413 MOXD1 monooxygenase, DBH-like 1 6q23.1-|23

NM_01552 0.316 0.001 0.100 2868265 LIX1 Lix1 homolog (chicken) 5q15 NM_15323 0.329 0.001 0.098 2669979 CX3CR1 chemokine (C—X3—C motif) receptor 1 3p21|3p21

NM_00117 0.278 0.005 0.095 2721959 SLC34A2 solute carrier family 34 (sodium phosphate), member 2 4p15.3-p15

NM_00117 0.354 0.000 0.091 3167110 ANXA2P2 annexin A2 pseudogene 2 9p13 NR_00357 0.335 0.001 0.084 3596147 GCNT3 glucosaminyl (N-acetyl) transferase 3, mucin, type 15q21.3 NM_00475 0.369 0.000 0.083 3129065 CLU clusterin 8p21-p12 NM_00183 0.347 0.000 0.080 2315918 ATAD3C ATPase family, AAA domain containing 3C 1p36.33 NM_00103 0.268 0.007 0.080 3020192 TES testis derived transcript (3 LIM domains) 7q31.2 NM_01564 0.343 0.000 0.080 4019160 KLHL13 kelch-like 13 (Drosophila) Xq23-q24 NM_00116 0.380 0.000 0.072 2602770 DNER delta/notch-like EGF repeat containing 2q36.3 NM_13907 0.327 0.001 0.066 3471753 C12orf47 chromosome 12 open reading frame 47 12q24.12 NR_015404 0.214 0.032 0.056 2898441 KAAG1 kidney associated antigen 1 6p22.1 NM_18133 0.265 0.007 0.062 2486927 ARHGAP25 Rho GTPase activating protein 25 2p13.3 NM_01488 0.300 0.002 0.062 3415320 XRT7 keratin 7 12q12-q13 NM_00555 0.251 0.011 0.061 2787902 GYPE glycophorin E (MNS blood group) 4q31.1 NM_19868 0.281 0.004 0.059 3020343 MET met proto-oncogene (hepatocyte growth factor receptor) 7q31 NM_00112 0.325 0.001 0.057 2414958 TACSTD2 tumor-associated calcium signal transducer 2 1p32-p31 NM_00235 0.240 0.015 0.057 3405587 GPRC5A G protein-coupled receptor, family C, group 5, member A 12p13-p12 NM_00397 0.277 0.005 0.057 2344888 CYR61 cysteine-rich, angiogenic inducer, 61 1p31-p22 NM_00155 0.349 0.000 0.055 3960061 RAC2 ras-related C3 botulinum toxin substrate 2 (rho family, 22q13.1 NM_00287 0.235 0.018 0.055 small GTP bi

2672140 LTF lactotransferrin 3p21.31 NM_00234 0.287 0.004 0.055 2879105 SPRY4 sprouty homolog 4 (Drosophila) 5q31.3 NM_03096 0.304 0.002 0.053 2864449 SERINC5 serine incorporator 5 5q14.1 NM_00117 0.331 0.001 0.049 3168938 POLR1E polymerase (RNA) I polypeptide E, 53 kDa 9p13.2 NM_02249 0.250 0.012 0.047 2356142 LIX1L Lix1 homolog (mouse)-like 1q21.1 NM_15371 0.257 0.009 0.047 3464860 DUSP6 dual specificity phosphatase 6 12q22-q23 NM_00194 0.382 0.000 0.047 3108489 LAPTM4B lysosomal protein transmembrane 4 beta 8q22.1 NM_01840 0.316 0.001 0.047 2374982 RNPEP arginyl aminopeptidase (aminopeptidase B) 1q32 NM_02021 0.286 0.004 0.044 3796620 DLGAP1 discs, large (Drosophila) homolog-associated protein 1 18p11.3 NM_00474 0.363 0.000 0.044 3662041 OGFOD1 2-oxoglutarate and iron-dependent oxygenase domain 16q12.2 NM_01823 0.284 0.004 0.043 containing 1 2323899 UBXN10 UBX domain protein 10 1p36.12 NM_15237 0.226 0.023 0.043 3332913 TMEM216 transmembrane protein 216 11q13.1 NM_01649 0.244 0.014 0.043 3954887 CHCHD10 coiled-coil-helix-coiled-coil-helix domain containing 10 22q11.23 NM_21372 0.339 0.001 0.043 3850445 CDKN2D cyclin-dependent kinase inhibitor 2D (p19, inhibits CDK4) 19p13 NM_00180 0.263 0.008 0.042 3232349 PFKP phosphofructokinase, platelet 10p15.3-p1

NM_00262 0.247 0.013 0.041 2881187 CSF1R colony stimulating factor 1 receptor 5q33-q35 NM_00521 0.240 0.016 0.041 3820443 ICAM1 Intercellular adhesion molecule 1 19p13.3-p1

NM_00020 0.245 0.013 0.040 3326826 FJX1 four Jointed box 1 (Drosophila) 11p13 NM_01434 0.384 0.000 0.040 2825629 TNFAIP8 tumor necrosis factor, alpha-induced protein 8 5q23.1 NM_01435 0.294 0.003 0.040 3868998 NKG7 natural killer cell group 7 sequence 19q13.41 NM_00560 0.243 0.014 0.039 3726154 ITGA3 integrin, alpha 3 (antigen CD49C, alpha 3 subunit of 17q21.33 NM_00220 0.263 0.008 0.039 VLA-3 receptor 3024025 MEST mesoderm specific transcript homolog (mouse) 7q32 NM_00240 0.291 0.003 0.038 2459352 WNT9A wingless-type MMTV integration site family, member 9A 1q42 NM_00339 0.237 0.017 0.037 3872335 ZNF416 zinc finger protein 416 19q13.4 NM_01787 0.283 0.004 0.037 2899437 BTN2A1 butyrophilin, subfamily 2, member A1 6p22.1 NM_07847 0.255 0.010 0.037 3734648 SLC16A5 solute carrier family 16, member 5 (monocarboxylic 17q25.1 NM_00469 0.279 0.005 0.037 acid transporte

3605395 ADAMTSL3 ADAMTS-llke 3 15q25.2 NM_20751 0.320 0.001 0.036 2435218 TDRKH tudor and KH domain containing 1q21 NM_00108 0.272 0.006 0.033 2876361 PITX1 paired-like homeodomain 1 5q31 NM_00265 0.246 0.013 0.033 2621881 P4HTM prolyl 4-hydroxylase, transmembrane (endoplasmic 3p21.31 NM_17793 0.293 0.003 0.032 reticulum) 2407985 HEYL hairy/enhancer-of-split related with YRPW motif-like 1p34.3 NM_01457 0.240 0.016 0.031 3270270 PTPRE protein tyrosine phosphatase, receptor type, E 10q26 NM_00650 0.255 0.010 0.031 3738471 RAC3 ras-related C3 botulinum toxin substrate 3 (rho family, 17q25.3 NM_00505 0.246 0.013 0.030 small G IP bi

3028217 — — — AK303101 0.243 0.014 0.030 3888383 SLC9A8 solute carrier family 9 (sodium/hydrogen exchanger), 20q13.13 NM_01526 0.299 0.002 0.030 member 8 2567583 RNF149 ring finger protein 149 2q11.2 NM_17364 0.304 0.002 0.030 3056264 ABHD11 abhydrolase domain containing 11 7q11.23 NR_026912 0.251 0.011 0.029 3261009 KAZALD1 Kazal-type serine peptidase inhibitor domain 1 10q24.31 NM_03092 0.251 0.011 0.029 2369484 TOR3A torsin family 3, member A 1q25.2 NM_02237 0.279 0.005 0.028 2931391 MTHFD1L methylenetetrahydrofolate dehydrogenase 6q25.1 NM_01544 0.299 0.002 0.028 (NADP+ dependent) 1-li

3361971 ST5 suppression of tumorigenicity 5 11p15 NM_00541 0.231 0.020 0.028 3623717 FLJ10038 hypothetical protein FLJ10038 15q21.2 NR_026891 0.277 0.005 0.028 2361342 SEMA4A sema domain, Immunoglobulin domain (Ig), 1q22 NM_02236 0.229 0.021 0.026 transmembrane domai

3051655 VOPP1 vesicular, overexpressed in cancer, prosurvival protein 1 7p11.2 NM_03079 0.229 0.021 0.025 3776504 TGIF1 TGFB-Induced factor homeobox 1 18p11.3 NM_17069 0.249 0.012 0.025 2692319 ADCY5 adenylate, cyclase 5 3q13.2-|21

NM_18335 0.200 0.044 0.025 2933392 SYMJ2 synaptolanin 2 6q25.3 NM_00389 0.283 0.004 0.024 3185593 BSPRY B-box and SPRY domain containing 9q32 NM_01768 0.279 0.005 0.023 3865998 PNMAL1 PNMA-like 1 19q13.32 NM_01821 0.234 0.019 0.023 2359885 SLC27A3 solute carrier family 27 (fatty add transporter), member 3 1q21.3 NM_02433 0.237 0.017 0.022 2714132 PDE6B phosphodiesterase 6B, cGMP-specific, rod, beta 4p16.3 NM_00028 0.272 0.006 0.022 3224087 TTLL11 tubulin tyrosine ligase-like family, member 11 9q33.2 NM_00113 0.248 0.012 0.021 3431892 SH2B3 SH2B adaptor protein 3 12q24 NM_00547 0.307 0.002 0.018 3193339 RXRA retinoid X receptor, alpha 9q34.3 NM_00295 −0.305 0.002 −0.025 3645901 NAT15 N-acetyltransferase 15 (GCN5-related, putative) 16p13.3 NM_02484 −0.298 0.002 −0.040 2942578 CCDC90A coiled-coil domain containing 90A 6p24.3-p23

NM_00103 −0.268 0.007 −0.044 3907507 C20orf165 chromosome 20 open reading frame 165 20q13.12 NM_08060 −0.219 0.028 −0.049 3305801 SORCS1 sortilin-related VPS10 domain containing receptor 1 10q23-q25 NM_05291 −0.272 0.006 −0.060 3021696 ASB15 ankyrin repeat and SOCS box-containing 15 7q31.31 NM_08092 −0.255 0.010 −0.102 3394412 THY1 Thy-1 cell surface antigen 11q22.3-q2

NM_00628 −0.235 0.016 −0.112 3635903 LOC388152 hypothetical LOC388152 15q25.2 BC054509 −0.212 0.033 −0.136

indicates data missing or illegible when filed

TABLE 5 CADI subscore comparisons between prog/non-progressor 3-month 12-month Progressors Non-Progressors Progressors Non-Progressors Parameter Mean ± SD Mean ± SD *p-value Mean ± SD Mean ± SD *p-value CADI 1.53 ± 1.18 0.86 ± 0.98 0.03 5.65 ± 2.47 0.96 ± 0.98 <0.0001 ct-score 0.56 ± 0.51 0.41 ± 0.50 0.29 1.53 ± 0.87 0.52 ± 0.50 <0.0001 cv-score 0.0 ± 0.0 0.02 ± 0.14 0.64 0.0 ± 0.0 0.0 ± 0.0 NA ci-score 0.44 ± 0.63 0.10 ± 0.30 <0.01 1.71 ± 1.11 0.16 ± 0.37 <0.0001 i-score 0.06 ± 0.25 0.08 ± 0.34 0.98 1.71 ± 0.92 0.06 ± 0.23 <0.0001 mm-score 0.0 ± 0.0 0.02 ± 0.14 0.61 0.25 ± 0.68 0.0 ± 0.0 0.01 g-score 0.28 ± 0.73 0.16 ± 0.58 0.47 0.06 ± 0.25 0.12 ± 0.52 1.00 *Mann-Whitney test

TABLE 6 Baseline clinical and demographic characteristics for GoCAR patient cohorts. Microarray RT-PCR patients patients (n = 101) (n = 45) *P- Characteristics: Mean ± SD (%) Mean ± SD (%) value Recipient age 46.90 ± 12.38 46.81 ± 11.52 0.69 Recipient race 0.96 Caucasian 66 (65.35) 33 (73.33) African American 15 (14.85) 3 (6.67) Other 20 (19.80) 9 (20.0) Recipient ESRD diagnosis 0.63 Diabetic nephropathy 33 (32.67) 10 (22.22) Hypertension 17 (16.83)  6 (13.33) Glomerulonephritis 22 (21.78) 15 (33.33) Polycystic Kidney 13 (12.87)  5 (11.11) Other 16 (15.84)  9 (20.00) Donor age 40.73 ± 16.80 44.87 ± 14.68 0.16 Donor race 0.72 Caucasian 80 (79.21) 42 (93.33) Non-Caucasian 21 (20.79) 3 (6.67) h/o Delayed graft function 9 (8.91)  5 (11.11) 0.54 Anti-HLA antibodies** 19 (20.21) 19 (42.22) <0.01 Class-I 19 (20.21) 19 (42.22) Class-II 4 (3.90) 12 (26.67) 3-month eGFR-creatinine 62.53 ± 17.90 59.27 ± 18.91 0.37 3-month Acute rejection^(#) 20 (22.7)  11 (28.94) 0.36 High/low CADI-12 40/61 18/27 1.00 High CADI-12 0.34 Mean ± SD 4.58 ± 2.25 4.00 ± 2.09 Median(IQR)   4 (3.0-5.0)     3 (2.75-5.0) Low CADI-12 0.96 Mean ± SD 0.48 ± 0.50 0.48 ± 0.51 Median(IQR)  0.0 (0.0-1.0)  0.0 (0.0-1.0) *P-value by Unpaired T-test (or non-parametric) and, Chi-square/Fisher's exact test. **94/101 & 38/45 patients had HLA antibodies measured. ^(#)86/101 & 40/45 patients had 3-month biopsy reported for histology

TABLE 7 Association of 10 principle components of 13 geneset with graft loss in Cox proportional hazard model PC coef exp(coef) se(coef) z p PC1 −0.396 6.73E−01 32.66 −0.0121 0.99 PC2 −6.845 1.06E−03 7 −0.9778 0.33 PC3 −0.931 3.94E−01 7.96 −0.117 0.91 PC4 −14.933 3.27E−07 5.03 −2.9692 0.003 * PC5 1.366 3.92E+00 3.87 0.3532 0.72 PC6 12.233 2.05E+05 5.14 2.38 0.017 * PC7 9.201 9.90E+03 4.44 2.0735 0.038 * PC8 0.824 2.28E+00 3.8 0.2166 0.83 PC9 −2.674 6.90E−02 5.18 −0.5159 0.61 PC10 −2.771 6.26E−02 4.02 −0.6889 0.49 Likelihood ratio test = 20.7 on 10 df, p = 0.023 n = 155, number of events = 11

TABLE 8 Association of demographic or clinical variables with graft loss in Cox proportional hazard mode Variable Coef Exp(coef) SE(coef) Z P ACR_M3_and_less 2.5635 1.30E+01 1.31E+00 1.96E+00 0.05 Delayed_Graft_Function 1.8058 6.08E+00 8.64E−01 2.09E+00   0.037 * M3_CADI −0.196 8.22E−01 2.84E−01 −6.89E−01  0.49 Donor_Status(Living vs deceased) 1.516 4.77E+00 1.39E+00 1.12E+00 0.26 HLA1_n 19.1431 2.06E+08 1.78E+04 1.08E−03 1   HLA1_ndsa 0.9569 2.60E+00 2.18E+04 4.39E−05 1   HLA2_n 15.5608 5.73E+06 7.23E+04 2.15E−04 1   HLA2_ndsa 34.0887 6.38E+14 7.34E+04 4.64E−04 1   Induction_Type_LND 0.0239 1.02E+00 1.37E+00 1.74E−02 0.99 Induction_Type_None −0.5606 5.71E−01 1.78E+00 −3.15E−01  0.75 Donor_Race: Black/African −0.5692 5.66E−01 2.15E+00 −2.65E−01  0.79 American Donor_Race: Hispanic −19.7123 2.75E−09 1.59E+04 −1.24E−03  1   Donor_Race: Pacific Islander −2.7581 6.34E−02 1.19E+05 −2.31E−05  1   Donor_Race: White/Caucasian −0.1417 8.68E−01 1.78E+00 −7.98E−02  0.94 Race: Black/African American −0.0731 9.29E−01 2.14E−00 −3.42E−02  0.97 Race: Hispanic 0.8838 2.42E+00 2.50E+00 3.54E−01 0.72 Race: Pacific Islander −16.8824 4.66E−08 1.12E+05 −1.51E−04  1   Race: White/Caucasian −1.4232 2.41E−01 1.58E+00 −9.00E−01  0.37 Donor_age 0.0189 1.02E+00 3.46E−02 5.45E−01 0.59 Age 0.0238 1.02E+00 4.54E−02 5.25E−01 0.6  * HLA antibody: dsa: donor specific antigen, reference; ndsa: non dsa antibody; n: no antibody Induction type: LD: Lymphocyte Depletion, reference; LND: Lymphocyte Non-Depletion; None: No Induction * The reference for Race: Asian Likelihood ratio test = 32.1 on 24 df, p = 0.123 n = 135, number of events = 10

TABLE 9 Validation of the GoCAR gene set in other kidney transplant cohorts. Genechip/ Sample Data Set Platform Size Outcome AUC Ref. Dataset 1 Affymetrix 282 Allograft loss 0.83 9 U133 Plus 2.0 Dataset 2 Affymetrix 24 CADI 0.972 10 U133 Plus 2.0

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The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and the accompanying figures. Such modifications are intended to fall within the scope of the appended claims. It is further to be understood that all values are approximate, and are provided for description. Patents, patent applications, publications, product descriptions, and protocols are cited throughout this application, the disclosures of which are incorporated herein by reference in their entireties for all purposes. 

1. A method for identifying a renal allograft recipient at risk for chronic allograft damage or interstitial fibrosis and tubular atrophy (IF/TA) comprising the steps of: (a) providing a biopsy specimen from the allograft; (b) providing an expression library as a comparison standard (c) isolating mRNA from the biopsy specimen; (d) synthesizing cDNA from the mRNA, producing a preselected gene signature set; (e) detecting the transcription level of a preselected gene signature set of step (d) (f) comparing the transcription level of the preselected gene signature set with the transcription level of a comparion standard, and (g) diagnosing the recipient as being at risk for chronic allograft damage or IF/TA if the transcription level of the preselected gene signature set is higher than the transcription level of the comparison standard.
 2. The method of claim 1 wherein the selected gene signature set comprises the genes KLHL13, KAAG1, MET, SPRY4, SERINC5, CHCHD10, FJX1, WNT9A, RNF149, ST5, TGIF1, RXRA and ASB15.
 3. The method of claim 2 which comprises treating the recipient to prevent chronic allograft damage or IF/TA if the transcription level of the preselected gene signature set is significantly higher than the transcription level of the comparison standard.
 4. The method of claim 3 wherein the treatment comprises administering an immunosuppressive agent to the recipient identified as being at risk for chronic allograft damage or IF/TA.
 5. (canceled)
 6. The method of claim 1 wherein the treatment comprises treating the recipient identified as being at risk for chronic allograft damage or IF/TA by administering an angiotensin converting enzyme to the recipient.
 7. The method of claim 1 which comprises using genes selected from the group consisting of Beta Actin (ACTB), 60S Ribosomal Protein PO (RPLPO), Glyceraldehyde 3-Phosphate Dehydrogenase (GAPDH) and 18s Ribosomal RNA as a negative control.
 8. A kit for identifying renal allograft recipients at risk for chronic allograft damage or IF/TA comprising a container having therein primers for a 13 member gene signature set and printed instructions for use.
 9. The kit of claim 8 further comprising a second container having therein primers for a set of housekeeping genes.
 10. The kit of claim 9 further comprising a third container having therein a buffer solution.
 11. A gene signature set for identifying patients at risk for chronic renal damage or IF/TA comprising the genes KLHL13, KAAG1, MET, SPRY4, SERINC5, CHCHD10, FJX1, WNT9A, RNF149, ST5, TGIF1, RXRA and ASB15.
 12. The method of claim 3 wherein the treatment comprises administering an anti-fibrotic agent to the patient. 13-15. (canceled)
 16. The method for selecting a renal allograft patient for treatment to reduce the risk of chronic allograft damage or IF/TA which comprises (a) providing a biopsy specimen from the allograft; (b) providing an expression library as a comparison standard (b) isolating mRNA from the biopsy specimen; (c) synthesizing cDNA from the mRNA, producing a preselected gene signature set; (d) detecting the transcription level of a preselected gene signature set of step (c); (e) comparing the transcription level of the preselected gene signature set of step (d) with the transcription level of a comparison standard and (f) selecting the patient for treatment if the transcription level of the preselected gene signature set is significantly higher than the transcription level of the comparison standard.
 17. The method of selecting a renal allograft recipient for treatment to reduce the risk of chronic allograft damage or IF/TA which comprises comparing the transcription level of a preselected gene signature set obtained from the allograft with the transcription level of a comparison expression library, and selecting the patient for treatment for allograft rejection or IF/TA if the transcription level of the preselected gene signature set is significantly higher than the transcription level of the comparison standard.
 18. The method of claim 16 which comprises treating the selected patient for allograft rejection.
 19. The method of claim 17 which comprises treating the selected patient for allograft damage.
 20. The method of claim 18 wherein the treatment comprises administration of an immunosuppressive agent.
 21. The method of claim lwhich comprises detecting the transcription level of a preselected gene signature set of step (c) with RT-PCR.
 22. The method of claim lwhich comprises detecting the transcription level of a preselected gene signature set of step (c) with nanostring,
 23. The method of claim lwhich comprises detecting the transcription level of a preselected gene signature set of step (c) with MiSeq.
 24. The kit of claim 8 further comprising a comparison standard. 